1. Field of the Invention
The invention relates to vehicles. More specifically, it relates to vehicles for use on a battlefield.
2. Discussion of the Prior Art
Essential qualities for a light to medium weight military vehicle are rapid maneuverability coupled with the ability to successfully negotiate difficult terrain. Also, such a vehicle must be reliable and resistant to damage from rough terrain, land mines, enemy fire and other hazards of the battlefield. The availability of operating transportation is often critical to the success of battlefield operations, and as a result, yet another criteria for a battlefield vehicle is that it be relatively simple and easy to repair when necessary. It should also be as lightweight as possible to allow for transport by air.
Battlefield vehicles have generally either been equipped with wheels or track drives as the primary driving means. Wheels offer speed and rapid maneuverability as an advantage. A disadvantage, however, is that a wheeled vehicle may become easily stuck in deep mud or other difficult terrain. Also, the rubber tires used with wheels are vulnerable to damage. By comparison, vehicles with a properly configured track drive can generally negotiate even the most difficult of terrain. The track drive is also normally more damage resistant. Generally, however, the track drive makes the vehicle slower and less maneuverable. Also, the suspension required for a full-time track drive can be heavy and complex, making for more difficult repairs. A vehicle for battlefield use that combines the advantages of wheeled and tracked vehicles while minimizing the disadvantages of each is a most desirable goal. Previous attempts to combine the advantages of wheels and tracks have not provided a vehicle suitable for operations on the modern battlefield.
U.S. Pat. No. 576,764 issued to Price, for instance, discloses a traction engine having an auxiliary endless track drive combined with road wheels and driven mechanically at the same speed as the wheels. The endless track is engaged with the ground at all times, limiting maneuverability and speed of the vehicle in all conditions. Another example of a vehicle with an auxiliary track drive can be found in U.S. Pat. No. 995,538 to Heverling, which discloses an auxiliary track drive that can be disengaged from the ground. This concept requires a complex mechanism for retracting the endless track assembly. Moreover, the wheels and tracks are each mechanically connected to the vehicle engine, relating the track speed to the engine speed and wheel speed. As a result, there is no selective adjustment of relative speed of the tracks to wheels, as is sometimes needed to traverse difficult terrain. A still further example can be seen in U.S. Pat. No. 3,469,553 to Gagne, which discloses an amphibious vehicle with an endless track and wheels. The track is normally out of contact with the ground, but serves to drive the wheels at all times. When the vehicle sinks into snow or other soft terrain, the track engages the ground and provides some traction assist. Again, the wheels and track are mechanically connected. Neither the wheels nor the track is vertically adjustable, providing no choice to the operator for selecting when the different driving means are to be used. Instead the operator must wait for the vehicle to become fully mired in the terrain before using the traction assist. Also, the track mechanism of this vehicle occupies a great deal of area within the vehicle hull, reducing available capacity and raising the vehicle center of gravity. These deficiencies of all of these examples, coupled with their generally complex and inflexible natures, make them unsuitable to be adapted for a modern battlefield vehicle.
What is needed is a vehicle combining the rapid maneuverability of wheels with the terrain negotiating ability of tracks and coupled with the desirable characteristics of: (a) having completely separate and adjustable wheel and track drives; (b) a simple, easily repairable, track assembly without heavy and complex suspension parts, that is selectively engagable when needed to negotiate difficult terrain or whenever desired; and (c) wheels that can be selectively disengaged from ground contact to effect weight transfer to the track, increasing traction and stability.